The present invention relates to a wind turbine with a suspension and such a suspension for attaching elongated members such as cables, cords, wires or the like, said suspension comprising a first clamping portion and a second clamping portion, said clamping portions being intended for clamping around the member, and where the first clamping portion and the second clamping portion may be displaced inwards against towards each other and by means of securing means may be secured around the item. The invention also relates to a holder for such suspension.
U.S. Pat. No. 5,195,704 describes a clamp for securing a cord or the like. The clamp comprises a body and a cover, each provided with surfaces for supporting the cord. Each part comprises a clamping portion and a through-going bead, extending within the surface of the clamping jaw. The cover is displaceable in relation to the body so that the clamping jaws are more or less tightly engaged. Thus, it is possible to secure cords with different diameters. The cover is displaced in relation to the body and is secured in relation to the body by means of a bolt.
However, this clamp has certain drawbacks. Because of the shape of the clamping jaws, where the inner surfaces of the clamping jaws have a partly circular cross-section with a given radius, it is not possible to secure cords with a smaller diameter as well as cords with a large diameter, and specifically not as well as cords with a diameter corresponding to the radius of the inner surfaces of the clamping jaws. Furthermore, the way that the body and the cover are mutually connected has the drawback that there is a risk of tearing off any insulation of the cords because of the pincers-movement made by the cover in relation to the body, when the two clamping jaws are being displaced towards each other.
U.S. Pat. No. 4,684,196 describes a clamp connector for holding of electrical wires and for connecting of these. The connector comprises a first and a second half portion which are mutually joined and which are provided with at least two corresponding grooves for taking up of the electrical wires. Each of the two half portions is provided with transverse bridging plates that are provided with sets of piercing teeth. The purpose of the connector is to provide a means that is capable of better securing the electrical wires, also even if the ends of the electrical wires are exposed to a permanent deformation when the ends are pushed together in the holder. Furthermore, it is a purpose that the connector itself is not exposed to deformation when the two half portions of the connector are mutually connected and tightened towards each other.
This connector has actually the complete opposite purpose than the present invention and accordingly this connector is provided with means that are very different to the means of the holder of the present invention. The purpose of the above-mentioned connector is to penetrate the insulation of the wires and the wires themselves in order to obtain the conducting contact between the ends of the wires and the transverse bridging plates. Thus, a severe and permanent deformation of not only the insulation but also of the wiring itself is established with the connector of the above-mentioned US-publication.
DE 2 650 145 describes a clamp for hanging up of electrical cables extending horizontally between masts. The clamp comprises an inner shelf clamping around the cable and an outer shelf surrounding the inner shelf. The inner shelf consists of two halves tightened together around the cable. Each of the two halves is provided with jaws together forming a substantially semi-circular cross-section, so that when the two halves of the inner shelf are squeezed together then a substantially circular cross-section is formed through which cross-section the electrical cable stretches. The purpose of the holder is however to provide a holder minimising the risk of water penetrating into the holder and which, if water nevertheless did pass into the holder, assures that the water is led out of the holder again.
This holder has more similarities with the present invention. However, still a substantial drawback is envisaged. Each of the two halves of the inner shelf has opposite end surfaces being pushed towards each other when the two halves of the inner shelf are being tightened together. There is a great risk of the insulation of the electrical wires being squeezed between these opposing surfaces. It is important to bear in mind, that the diameter of the electrical wire may vary depending on the manufacturer of the cables and depending on the type of cable and due to different dimensions depending on temperature and humidity. Especially in the case where the two halves are completely joined and where the opposing surfaces are abutting each other when the halves are joined, then there is an even greater risk of the insulation being squeezed and damaged.
U.S. Pat. No. 5,794,897 describes a hanger for supporting transmission lines such as coaxial cables and the like used in antenna systems. The hanger comprises a clamping structure with two gripping elements. The gripping elements of the clamping structure grip the coaxial cables by means of notches provided on gripping surfaces of the gripping elements. This is accomplished by securing means such as bolt and nut, which tighten the two gripping elements together. The gripping elements are also provided with snapping elements for connecting said gripping elements so that the clamping structure may be used for initially loosely clamping the cables and subsequently firmly clamping the cables when the securing means are tightened.
The document describes the possibility of gripping cables by having beads on gripping surfaces of gripping elements. However, the clamping structure still has the great disadvantage that the outer insulation of the cables may be damaged when the gripping elements are tightened. Because of the expressed need for firstly loosely securing and subsequently firmly securing the cables to the clamping structure, snapping means are provided. These may however squeeze the insulation when the gripping elements are firmly tightened around the cables. Furthermore, there is no mentioning of the special problems occurring within wind turbine towers where the cables may be twisted.
U.S. Pat. No. 4,545,728 describes a wind turbine with yaw spring return means for returning the nacelle of the wind turbine from a position to which it has been turned to the initial position in order to prevent excessive twisting of the power cables and control cables. The power cables and control cables extend loosely and linearly downwards from the nacelle through a passage constituted by an annular bearing to the tower. When the nacelle rotates in relation to the tower, the cables will twist as well. When the nacelle by means of the yaw spring returns to its initial position the cables will unwind.
This document does however not disclose special means for suspending the cables extending from the nacelle downward through the passage to the tower. Thus, with no special suspension means and with a twisting of the cables, then there is a great risk of the cables disconnecting from whichever attachment means they may be connected to. Also, cables extending form the nacelle and downwards through high towers will experience that the weight of the cables together with only a slight twisting of the cables may cause the cables to disconnect in response to a combination of the load from the weight of the cables just added a small force from the slight twisting of the cables.
It is the object of the present invention to provide a suspension capable of securing cords, cables, wires, hoses and the like with varying diameters with the same degree of securing, but also securing these items in a better way and especially a suspension for suspending the items vertically. Moreover, it is the object of the invention to provide a suspension without the risk of damaging the items or the insulation of the items.
The object is achieved by a wind turbine having a first suspension characterised in that the wind turbine further comprising at least a first suspension being suspended by the nacelle, the first cable suspension defining substantially vertically extending supporting surfaces, the outer surface of each of said elongated members such as electrical power cables for a longitudinal length of at least four times the mean outer diameter of the member being in abutting contact with and squeezed between at least two of each supporting surfaces so that a substantial part of the weight of the member is supported by the first suspension. The object may also be obtained by the suspension itself before installation in the wind turbine.
The object may also be achieved by a wind turbine having a second suspension characterised in that the wind turbine further comprising at least a first suspension being suspended by the nacelle, the first cable suspension defining substantially vertically extending supporting surfaces, the outer surface of each of said elongated members such as electrical power cables for a longitudinal length of between one and two times the mean outer diameter of the member and that the vertically extending supporting surfaces are provided with beads, and the member being in abutting contact with and squeezed between at least two of each supporting surfaces so that a substantial part of the weight of the member is supported by the first cable suspension. The object may also be obtained by the suspension itself before installation in the wind turbine.
By the present invention a means is provided for suspending elongated members such as electrical power cables, hydraulic hoses, ropes and the like which eliminates the risk of as example cables detaching from the nacelle causing failure in delivering the electrical power from the generator system of the wind turbine to the user. This is especially a risk in tall wind turbines that are becoming more and more common because of an increasing demand for wind turbines with larger and larger electrical capacity. Also, when using wind turbines with higher towers there is the risk of the electrical cables twisting inside the tower when the nacelle is pivoted in relation to the tower. In the following reference will mainly be made to electrical power cables as an example of elongated members to be suspended. However, the reference to electrical power cables does not limit the type of elongated members that the invention may be used for.
By letting the clamping portions extend around each other and by letting the clamping portions being assembled linearly and by letting the inner surface of the clamping portions extend in continuation of the inner surface of the jaws on the first clamping portion, it is achieved that no pincers-movement will occur when the clamping portions are assembled around e.g. the cable. Moreover it is achieved that it is possible to leave a large part of the inner surface of the clamping portions free so that the clamping around the cable can take place independently of the mutual engagement between the clamping portions.
In a preferred embodiment of invention the suspension is shaped in such a manner that the inner surface of the first clamping portion has a substantially semicircular contour, that the inner surface of the second clamping surface has a substantially semicircular contour, and that in a first application situation the clamping portions are secured so that the inner surfaces of the two clamping portions form a through-going hole which is circular when the clamping portions are assembled, and in a second application situation are secured so that the inner contour of the inner surfaces of the two clamping surfaces form a through-going hole which is oval when the clamping portions are assembled.
By providing through-going holes between the jaws on the clamping portions, being either round or oval, with said clamping portions it is made possible to secure e.g. cables with different diameters. In a preferred embodiment the suspension is characterised in that the suspension comprises a first clamping portion and furthermore comprises a first embodiment of a second clamping portion and a second embodiment of the second clamping portion, and that both the first embodiment and the second embodiment of the second clamping portion each are capable of co-operating with the first clamping portion, and where the through-going hole is substantially round when the first clamping portion co-operates with the first embodiment of the second clamping portion, and the through-going hole is substantially oval when the first clamping portion co-operates with the second embodiment of the second clamping portion.
By using the said first clamping portion but various second clamping portions, it is possible to obtain same large variation in diameter of e.g. those cables which the suspension is capable of securing. It is an advantage that only a single embodiment of the first clamping portion is capable of co-operation with various embodiments of the second clamping portion as it is then possible to retain the first clamping portion attached to e.g. a holder, and at the same time it is possible to replace the second clamping portion in order to secure e.g. different cables with different diameters.
The clamping portions according to the present invention are preferentially manufactured and are preferentially used as separate clamping portions. In an alternative embodiment, by the manufacture and the use of the clamping portions it will however be possible to join the first clamping portion with the second clamping portion by means of a kind of hinge device. This may have the advantage that already at the manufacture it is made easier to figure out, in connection with the later use, which clamping portions belong together, and that the first clamping portion and the second clamping portion are already joined together when the cable are mounted between the clamping portions, and the ears of the clamping portions are subsequently squeezed together by means of the bolts which extend through the holes in the ears.
Moreover, it will be possible to join a plurality of first and a plurality of second clamping portions so that a row of first clamping portions and a row of second corresponding clamping portions are formed. This opens up the possibility of delivering the clamping portions in tapes comprising several clamping portions of the same type. The type of clamping portion, which is suitable, can then be broken off or cut off the tape with the clamping portion of the type in question. It will also be possible to provide a combination of connections between a first clamping portion and a second clamping portion and connections in a tape partly between a plurality of first clamping portions and partly between a plurality of second corresponding clamping portions.
In a preferred embodiment a plurality of cable spacing devices are arranged between the electrical power cables with a vertical spacing between neighbouring spacing devices, each spacing device being arranged so as to maintain the power cables in a constant position in a horizontal plane of the spacing device with a mutual spacing between the cables.
By using spacing devices it is intended to keep a distance between the cables. Because of the electrical current running through the cables the cables are slightly heated. However if perhaps six cables are hanging from the nacelle and down through the tower, the heating will take place of all six cables at the same time. In this case it is especially necessary to maintain a distance between the cables. It is also necessary to maintain a distance between the cables in order to eliminate the risk of wear of the insulation of the cables. If the cables are passed down through the tower in a bundle the cables will slide along each other when the nacelle is pivoting in relation to the tower. Using spacers ensures that this mutual sliding is avoided.
In a further preferred embodiment the plurality of electrical power cables forms a down-hanging curve and is secured to the stationary part of the wind turbine at a vertical position above the lowest part of the curve, the vertical extent of the loop at the reference position of the nacelle being of a magnitude sufficient to ensure that the cable will not be exposed to excessive longitudinal tension due to the relative shortening of the cable caused by twisting of the cable during pivoting of the nacelle.
By securing the cables to the stationary part as example by using a cable support device that is secured to the inner wall of the tower, the cables will be led down through most of the tower along the inner wall of the tower. This makes it possible to eliminate the risk of the cables twisting excessively because the cables are hanging freely in a downwards curve before being led past the suspension, said downwards curve taking up the tensioning of the cable when the nacelle is pivoting in relation to the tower. Also, it eliminates the inconvenience of having the cables to take up space in the center of the tower.
Further scope of the applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.